counselling in practice
The articles in this series are independently researched and compiled by PSA commissioned authors and peer reviewed.
The scourge of scabies
Continuing Professional Development
By Nerida Firth
Learning objectives
After reading this article you should
be able to:
• Describe the cause, mode of
transmission and symptoms of a
scabies infestation.
• Advise on appropriate therapy
for scabies and provide key
counselling points.
• Understand the need for
vigilant monitoring for scabies
infestations in residential care
facilities, and the necessity for
prompt treatment to prevent
large outbreaks throughout a
facility.
Competency standards (2010)
addressed:
6.1.1, 6.1.2, 6.3.1, 6.3.3, 7.1.4
Accreditation number:
CAP110101a
Case study
Mrs GW presents to your pharmacy
with the news that the residential care
facility where her mother resides is
experiencing a scabies outbreak. She
is seeking information about scabies,
and advice regarding treatment.
Key questions to answer
Vol. 30 – January #01
What is scabies?
Nerida Firth is a Pharmacy Lecturer at the
School of Pharmacy and Molecular Sciences,
James Cook University, Townsville.
36
Scabies is an infectious dermatological
condition caused by Sarcoptes scabiei
variety hominis, an eight-legged
parasitic mite that is barely visible to
the human eye. The female mite is
0.3–0.4 mm long and 0.25–0.35 mm
wide, while the male is less than half
that size. These mites cannot jump or
fly, but they can crawl across warm
skin at a rate of 2.5 cm per minute.1,2
The scabies mite life-cycle is
completed entirely on humans and
consists of four stages – egg, larva,
nymph and adult. Only the female
mite burrows into the outer layer of
skin, where she lays up to three eggs
a day. The male mite spends its time
searching for an unfertilised female.1–3
Two to three days after an egg is laid
by a fertilised female in an epidermal
burrow, it hatches into a larva which
migrates to the surface of the skin.
This larva moults into a nymph
before becoming a mite. The entire
maturation process (from egg to mite)
lasts approximately 15 days.1–3 In a
classic case of scabies, a patient may
be infested with anywhere from five
to 15 mites.2
Submit your answers online at www.psa.org.au and receive automatic feedback
The characteristic symptom of scabies
is intense itching due to both the
infestation and a hyper-reaction to the
mite and its products (egg cases and
faecal pellets). On initial infestation,
onset of symptoms occurs after an
incubation period of 2–6 weeks,
during which time sensitisation
occurs as a result of an adaptive
immune response. If reinfested,
symptoms may develop within one
to four days, as the immune system
recognises the mite antigens and
responds immediately.2–4
Identification
Positive identification may be
confirmed by microscopically
examining skin scrapings for the
presence of mites, or their eggs
and faeces. However, as patients
with classic scabies have low mite
populations, a scraping of a burrow
may contain no traces of mites at all.2,7
If microscopic analysis of scrapings
returns a negative result, it may be
practical to treat with a scabicide
anyway and observe for a response
to treatment.9
Identification of scabies is difficult as a
patient’s symptoms may be subtle and
vary from the clinical norm. Burrows
are not always visible and may be
obscured by scratches, and the rash
may be on the trunk away from burrow
sites. If the patient does not fall
into a risk group, and scabies is not
expected to be present, misdiagnosis
may occur.3,9
Itching is often worse at night when
the patient is in bed or after a hot
bath, as the body is warmer and
the mites are more active. This
intense itching may disrupt sleep.3
Scratching often leads to secondary
bacterial infections. Nodules may
develop on the elbows and on the
penis and scrotum and manifest as
firm, dull red or brownish masses.
These lesions may persist for
months after successful scabicidal
treatment.3 Thick crusting and scaling
of the skin is characteristic of crusted
scabies, although it is sometimes
misdiagnosed as psoriasis.3
How is scabies transmitted?
Transmission of scabies is by direct
skin contact with an infested person.
The scabies mite cannot fly or jump,
so being in close proximity does not
lead to transmission. A dislodged
mite uses heat and odour to find
a new host. For the stimuli to be
strong enough, close skin contact of
approximately 20 minutes is thought
to be required. Examples of this
include holding a baby, sleeping in the
same bed and sexual intercourse.3,6
Brief contact such as a quick
handshake is generally not sufficient
for transmission.
Crusted scabies is more easily
transmitted than classic scabies due
to the presence of large numbers of
mites.3,5 In these cases, brief skinto-skin contact as well as fomites
(items such as bed linen, towels
and undergarments, with which an
infested person has been in contact)
can also transfer the parasitic mite.5
The higher the parasite burden, as is
the case with crusted scabies, the
greater the risk that mites will be
shed into fomites. The scabies mite
Scabies cannot be caught from
animals.7 The scabies mite that causes
mange in cats and dogs cannot
reproduce on humans. While these
mites may cause local irritation on a
human for several days, the infestation
is self-limiting and does not need
treatment.1,3,8
How can transmission
be prevented?
Immediate diagnosis of scabies must
be made to prevent spread. Anyone
who has had close physical contact
with the patient should be notified and
treated with a topical scabicide. If the
patient has crusted scabies, where
even minimal contact is a concern,
then all contacts should be notified.
All clothes, bed-linen and towels
with which the patient has come
into contact in the 72 hours before
diagnosis must be laundered in a hot
wash (at least 60ºC), placed in a hot
dryer for 30 minutes, or dry-cleaned.
Items that cannot be washed should
be sealed in a plastic bag and left for
seven days and then laundered.2,6–8,12
Minimising close physical contact
between the patient and others in
closed community or institutional
settings is recommended to prevent
further spread. This includes
excluding a young patient with classic
scabies from school or childcare, or
assigning a specific cohort of staff
to attend to patients with crusted
scabies in aged care facilities and
hospitals.1,7,8,14,15 Patients diagnosed
with crusted scabies in these aged
care facilities and hospital settings
may need to be isolated due to the
difficulty associated with effective
treatment.4,9,14,15
When is treatment of
scabies recommended,
and for whom?
Vol. 30 – January #01
Immediate and correct identification
of both forms of scabies is imperative
to prevent further infection. This
is especially critical for patients in
institutional settings such as hospitals
and residential care facilities.3,8
Scabies is characterised by intense
itching and a red papular rash. The
thin, slightly elevated, wavy greywhite burrows are specific for scabies,
but are rarely visible to the naked eye
and are often absent. The burrows
are commonly found in finger webs,
between toes, in the flexures of the
wrist and elbow, the armpits, groin,
buttocks, the lower abdomen, male
genitals and the area surrounding the
nipples in women.2,8 Infestation of
the face, head, palms and soles is not
often seen in adults, but is common
in infants.4
can survive off a human host for up
to 24–36 hours in an average room
environment.3,4,9 However, conditions
of higher humidity and lower
temperature may prolong this period.11
Therefore, fomites should be viewed
as infectious for a conservative
2–3 days after being in contact with
an infested person.6,7
Continuing Professional Development
Crusted (or Norwegian) scabies is
a more severe infestation of the
Sarcoptes scabiei mite and occurs
in elderly, immunosuppressed,
debilitated and institutionalised
patients, and in Indigenous Australian
communities. A patient with crusted
scabies may host thousands to
millions of mites, and is covered
in a scaly, crusted rash, although
itching may be absent.4,8 The extent
of the infestation is generally due to
the compromised immunity of the
patient, although cases reported in
Indigenous Australian communities
appear to occur even when there has
been no diagnosed immune deficiency
to date.4,5
What are the symptoms of
scabies?
On confirmation of a scabies
diagnosis, all of the patient’s close
physical contacts and members of
the affected household (and their
close physical contacts) must be
37
counselling in practice
The articles in this series are independently researched and compiled by PSA commissioned authors and peer reviewed.
Vol. 30 – January #01
Continuing Professional Development
treated at the same time to prevent
reinfestation.8,11 Even if these contacts
are asymptomatic, they may still be
infested and in the incubation stage.
Anyone who comes into close contact
with the patient until 24 hours after
scabicidal treatment should also be
treated, as should anyone who has
had prolonged contact with bedlinen, clothing or towels which the
patient has used 48–72 hours before
diagnosis.2,6,7,12
In an aged care facility or hospital
with a diagnosed crusted scabies
case, the nursing, cleaning and
laundry staff should be considered
contacts and therefore should be
treated appropriately with a topical
scabicide.4,9,12 If these staff work
at several facilities, monitoring
and treatment of scabies cases is
necessary at those places also.9,12,14
Outbreaks often coincide with
the arrival of a new patient with
undiagnosed crusted scabies, and
diagnosis is only established after a
widespread infestation occurs.9,14 It
is recommended that all identified
patients in a closed community
setting are treated within the same
24–48 hour period to prevent the
reinfestation of treated patients by
those who are yet to be treated.10,12,15
How is scabies treated?
Permethrin 5% cream/lotion (Lyclear/
Quellada Scabies Treatment) is the
agent of choice for most scabies
infections, due to its high level of
safety and efficacy.1,3,9,10 Although
benzyl benzoate is an effective
alternative it can be quite irritating to
the skin, and poor patient adherence
to the treatment regimen is also
an issue. Benzyl benzoate 25%
emulsion (Ascabiol, Benzemul) is
therefore reserved for second-line
therapy when a patient is allergic to
permethrin, or permethrin treatment
fails. Despite not being approved
for treatment in this age group, the
recommended treatment for children
under six months of age is permethrin
5% cream, applied to the entire skin
surface (including the scalp, avoiding
the eyes and mouth and covering
the hands with mittens) and left on
for eight hours. Clinician discretion
is required, and if the risks outweigh
the benefits then sulfur 10% in white
soft paraffin or crotamiton 10% cream
(Eurax) may be applied once daily for
2–3 days.9
38
Counselling points for effective
use of permethrin 5% cream1,9
• Apply topically to dry skin from the
neck down at night after bathing
• Leave cream on overnight (or for
8–12 hours) and wash off the next
morning
• Suitable for adults and children over
the age of six months
• Treatment of choice for pregnant
and lactating women
• Reapply treatment in seven days
to ensure complete eradication of
newly hatched mites.
Recommended permethrin doses
– approximate amounts for a
single treatment.1,9
Adult
up to one tube
5-12 years
up to half a tube
1-5 years
up to one-quarter of a
tube
<1 year
up to one-eighth of a
tube
Counselling points for effective
use of benzyl benzoate 25%
emulsion1,9
• Test on small area of skin for 10
minutes before using
• Apply topically to dry skin from the
neck down at night after bathing
• Leave treatment on for 24 hours
and wash off well
• For children under two years of
age, dilute 1 part emulsion with 3
parts of water
• For children between two and
12 years of age, and adults with
sensitive skin, dilute emulsion with
equal parts of water
• Reapply treatment in seven days
to ensure complete eradication of
newly hatched mites.
Irrespective of the topical treatment
chosen, correct use and vigilant
adherence is imperative for
successful treatment. Important
practice points that should be
emphasised to all patients include:
• Reapply treatment to hands if
they are washed during treatment
period.
• Pay particular attention to ensure
complete coverage of hands and
genitalia. A nailbrush should be
used to ensure medicament is
applied under nails.
• Apply treatment to the face,
scalp, neck and ears in infants
(under two years old), older
adults (over 55 years of age),
immune‑compromised patients,
patients who have experienced
treatment failure previously or
those with atypical or Norwegian
(crusted) scabies.
• Take care to avoid spreading
treatment into eyes and onto
mucous membranes.
• All family members and close
physical contacts should be
treated simultaneously to reduce
chances of re-infection.6,7,9,11
Crusted scabies requires a more
vigorous treatment regimen due
to the high mite population, and
involvement of a dermatologist or
an infectious diseases physician
is recommended. Patients may be
treated with regular applications
of a scabicide, or oral ivermectin.
The standard dose of ivermectin for
patients aged five years and over
is 200 µg/kg, while the frequency
of dosing depends on the severity
of the case:9
Severity
of crusted
scabies
Frequency of dose
Less severe
days 1 and 8
Moderately
severe
days 1, 2 and 8
Severe
days 1, 2, 8, 9 and 15,
with 2 further doses
on days 22 and 29
for extremely severe
cases
Patients should be warned that
itching may continue for up to three
weeks after successful treatment.
It is important that patients do not
reapply treatment after the first two
applications.9 Instead, they may
apply a moderately potent topical
corticosteroid to the rash two to
three times a day.9 Cool baths
may be soothing, and avoiding hot
baths may prevent worsening of
itch. Concurrent application of a
simple emollient may also provide
some relief.7,9
Scabies nodules may last for months
after the infestation is eradicated;
however, a topical corticosteroid
may be useful to minimise their
size. In the case of persistent
nodules, intralesional corticosteroids
are sometimes administered to
hasten resolution.9 Secondary
infections should be treated as for
impetigo, with either dicloxacillin or
flucloxacillin.9,11,13
Submit your answers online at www.psa.org.au and receive automatic feedback
Is follow-up treatment
necessary?
What are the consequences
if scabies is left untreated?
All scabicides have a higher
success rate if repeat applications
are used on two occasions,
seven days apart. If treatment
with permethrin fails, then benzyl
benzoate should be used.9
Left untreated, the red papules that
form around the burrow entrances
may develop into vesicles and
bullae. With time these may become
secondary scabies lesions, which
include excoriations, eczematisation,
crusts and secondary infections.2,3
Streptococcus pyogenes that resides
on the skin is primarily associated with
secondary bacterial infections, as is
Staphylococcus aureus.3,4 Cellulitis,
boils and lymphangitis can result as a
consequence of these infections. Acute
post-streptococcal glomerulitis is an
observed consequence of secondary
infections of scabies with S. Pyogenes.
The high incidence of rheumatic
fever in indigenous communities is
suggested to be attributable to this
same secondary infection.3,4 Both
streptococci and staphylococci bacteria
have been cultured from mite faecal
pellets and skin burrows, suggesting
that the mites themselves may
contribute to secondary infection.4
Is treatment necessary if
patient is asymptomatic?
Anyone with symptoms of scabies
after contact with a patient
diagnosed with either classic or
crusted scabies should be treated
with the same regimen as the
patient.12 Asymptomatic persons
who have had close physical contact
with a diagnosed patient should be
informed of their possible exposure
and advised to undertake preemptive treatment.11,12 Similarly,
these people should notify their
close physical contacts to warn them
of the possibility of infection and
need for treatment.3,8,11,12,15
From an environmental health
perspective, untreated scabies
increases opportunistic spread
of infection and is particularly
problematic in an aged care
facility or hospital. In these closed
community settings it is common for
numerous cases to be encountered
simultaneously.1,2,4
Does this scabies outbreak
mean that the residential aged
care facility is of poor quality?
Scabies outbreaks in residential
facilities and hospitals are not an
indication of poor quality, just as
scabies is not a result of poor hygiene
or poor standards of care.4,8
Case study
Mrs GW should be advised that her
mother, the other residents and
staff at the residential care facility
should all be treated immediately.
All residents should be assessed to
determine whether any have crusted
Vol. 30 – January #01
39
counselling in practice
The articles in this series are independently researched and compiled by PSA commissioned authors and peer reviewed.
scabies in an attempt to determine
the source of the outbreak. Mrs GW
should treat herself and her family
with topical permethrin, and wash all
fomites in a warm wash cycle. She
should also be advised that anyone
who has had close contact with her
family since she visited her mother
should be notified and advised to
discuss the need for treatment with
their pharmacist.
Continuing Professional Development
Key learning points
Scabies infestations are quickly
spread through prolonged,
direct contact. Therefore,
immediate identification of
cases is imperative, as is correct
adherence to prescribed treatment.
Permethrin is the treatment of
choice due to its high level of
efficacy and low level of toxicity,
and is suitable in pregnant and
lactating patients. Once identified,
everyone who has had close
physical contact with the infested
patient or their fomites must be
treated immediately, even if they
are asymptomatc. This prompt
action will reduce the chance
References
1. Department of Health, State Government of Victoria.
Scabies. [Online] 2008 [cited 2010 Oct 6]. At: www.
health.vic.gov.au/ideas/bluebook/scabies
2. Chosidow O. Scabies. NEJM 2006 Apr
20;354(16):1718–27. At: www.nejm.org/doi/
full/10.1056/NEJMcp052784
3. Heukelbach J, Feldmeier H. Scabies. Lancet 2006
May 27;367:1767–74.
4. McCarthy JS, Kemp DJ, Walton SF, Currie BJ.
Scabies: more than just an irritation. Postgrad
Med J 2004;80:382–7. At: http://pmj.bmj.com/
content/80/945/382.full
5. Division of Parasitic Diseases, CDC. Scabies – risk.
[Online] Centres for Disease Control and Prevention
2008. At: www.cdc.gov/scabies/risk.html [cited 2010
Oct 06]
6. Melbourne Sexual Health Centre. Scabies. [Online]
Better Health Channel 2010. At: www.betterhealth.
vic.gov.au/bhcv2/bhcarticles.nsf/pages/Scabies
[cited 2010 Oct 06].
7. Department of Health, State Government of Victoria.
Scabies information sheet. [Online] 2008 [cited 2010
Oct 6]. At: www.health.vic.gov.au/ideas/bluebook/
scabies_info
Questions 1. Which statement is incorrect
with regard to crusted
(Norwegian) scabies?
a) Crusted scabies predominantly
affects the elderly,
immunosupressed or
institutionalised patients.
b) Patients with crusted scabies are
infested with the Sarcoptes scabiei
mite, as are patients with classic
scabies.
c) Patients with crusted scabies are
treated with both ivermectin and a
topical scabicide.
d) A patient with crusted scabies is
generally infested with twice as
many mites as patients with classic
scabies.
Vol. 30 – January #01
of further transmission, and of
previously treated patients being
reinfected. Closed community
settings, such as residential
care facilities and hospitals, are
common settings for scabies
outbreaks because transmission is
fast, and the majority of residents
fall into the risk category for
crusted scabies.
2. Which statement is correct with
regard to the symptoms of a
scabies infection?
a) Scabies is characterised by
intense itching, red papules and
thin, wavy grey‑white burrows may
also be present.
b) Scabies nodules do not develop on
the elbows, penis and scrotum.
40
8. Department of Health, Government of South Australia.
Scabies: Prevention and treatment. [Online] 2008 [cited
2010 Oct 11]. At: www.health.sa.gov.au/pehs/PDFfiles/ph-factsheet-scabies.pdf
9. Therapeutic Guidelines. Scabies (Sarcoptes scabei
var. hominis). [Online]. 2009. Available from: eTG31;
2010. [cited 2010 Oct 06].
10. eAMH: Scabies monograph. Australian Medicines
Handbook; Jan 2010.
11. Commens C, Sullivan JR. A-Z of skin: Scabies. [Online].
Australasian College of Dermatologists; 2001. At: URL:
www.dermcoll.asn.au/public/a-z_of_skin-scabies.asp
[cited 2010 Oct 06].
12. Department of Health, State Government of Victoria.
Guide to scabies management in residential care
facilities. [Online] 2008 [cited 2010 Oct 6]. At: www.
health.vic.gov.au/ideas/bluebook/scabies_guide
13. Therapeutic Guidelines. Impetigo. [Online]. 2009.
Available from: eTG31. Therapeutic Guidelines; 2010.
[cited 2010 Oct 26].
14. Division of Parasitic Diseases, CDC. Scabies – Health
care providers – Control. [Online] Centres for Disease
Control and Prevention 2008. At: www.cdc.gov/
scabies/hcp/control.html [cited 2010 Oct 06]
15. Division of Parasitic Diseases, CDC. Scabies – Health
care providers – Crusted scabies cases. [Online] Centres
for Disease Control and Prevention 2008. At: www.cdc.
gov/scabies/hcp/crusted.html [cited 2010 Oct 06]
A score of 4 out of 5 attracts 1 CPD credit.
c) The itching associated with scabies
is due to the presence of the mite,
and ceases three to seven days after
application of a scabicide.
d) Thick scaling and weeping nodules
are characteristic of crusted
(Norwegian) scabies.
3. Which statement is correct with
regard to transmission of the
scabies mite?
a) Scabies can be caught from animals.
b) Crusted scabies can be transmitted
via brief, close contact and fomites.
c) Dislodged scabies mites use sight
and hearing to find a new host, and
therefore close contact is required
for these stimuli to be strong
enough.
d) The scabies mite can jump from one
person to another.
4. Which statement is correct with
regard to treatment options
for scabies?
a) Poor patient compliance is a
limitation to the use of benzyl
benzoate 25% emulsion.
b) Permethrin is approved for use in all
age groups.
c) Treatment should be reapplied
21 days after initial application of
a scabicide to ensure complete
eradication of the scabies mite.
d) Permethrin is not a suitable treatment
for pregnant and lactating women.
5. Which statement is not an
appropriate counselling point
for patients?
a) Reapply treatment to hands if they
are washed during treatment period.
b) Pay particular attention when
applying treatment to hands and
genitalia. A nailbrush should be used
to ensure medicament is applied
under nails.
c) In most cases treatment needs
to be applied to the entire body,
including face, scalp, neck and ears
and left on for an advised period of
time (permethrin: 8–12 hours; benzyl
benzoate: 24 hours).
d) All family members and likely
contacts should be treated
simultaneously to reduce chances of
re-infection.